Now, run namebench, with those DNS servers, plus any others you want to test. I added 1.1.1.1 and 8.8.8.8 (Google DNS). NOTE: this is going to use your Google Chrome browsing history to fire off a bunch of queries. If you don’t use Chrome, the resulting data won’t be very useful.

That runs for a while then dumps a bunch of output, and should open a web browser with even more. The “open a web browser” part didn’t work for me, but you can find the webpage it produces and open it yourself.